This invention relates to a chain cover which is mounted on a roller chain to cover a top and both sides of the chain, and provides a flat transporting surface.
Such chain covers are shown in JP patent publications 8-121542 and 8-231017.
The chain cover of the former publication has a top cover (web cover) covering a top of a chain, and side covers (opposed side walls) provided on both sides of the top cover to cover sides of the chain. The chain cover is mounted on the chain by fitting coupling pins of the chain into two shaft holes formed in each side cover. A load of articles being transported by the chain, that is applied to the top cover, is borne by the coupling pins.
The chain cover of the latter publication has a top cover having a length corresponding to one pitch of a chain. From both sides of the top cover, side covers extend which have a convex arcuate front edge and a concave arcuate rear edge that are concentrical with coupling pins of the chain. In an inner surface of each side cover, a groove is formed for engaging a pin-link plate with coupling pins. Two kinds of such cover blocks having different shapes of the grooves are alternately arranged and mounted on the chain.
With the chain cover of JP patent publication 8-121542, since a load applied to the top cover is borne by the coupling pins, it is necessary to increase an amount of insertion of the coupling pins into the shaft holes to bear the load stably. Thus, a roller chain on which the chain cover is to be fitted is also a special article. Further, it is difficult to attach and detach the chain cover on and from the roller chain.
In contrast, the chain cover of JP patent publication 8-231017 has a shape corresponding to one pitch of the chain. Thus, the above problem is substantially solved. But, since such covers are used with two different kinds of cover blocks combined, they are disadvantageous in terms of cost. It is also troublesome to maintain and attach and detach the cover blocks. Also, since it is necessary to attach and detach the cover blocks by markedly bending roller links and pin links of the chain, it is impossible to replace any damaged cover without dismounting the chain, from sprocket wheels.
Further, the chain cover of this publication cannot completely eliminate a bending restriction of the chain. Thus, a turning radius of the chain with the cover mounted thereon is larger than that when the cover is not on the chain.
An object of this invention is to provide a chain cover which solves these problems.
According to this invention, there is provided a chain cover comprising a top cover having a length substantially equal to a pitch of a roller chain for covering a top of the chain, and side covers extending from both ends of the top cover for covering sides of the roller chain. Each side cover has a shaft hole for receiving a coupling pin of the chain, a convex arcuate front edge that is concentric with the shaft hole, a concave arcuate rear edge opposed to the front edge, and a tapered guide surface tapering from an inner surface of the side cover below the shaft hole. The top cover is supported by roller links of the chain when the chain cover is mounted on the roller chain.
Preferably, a bottom surface of the side cover is a straight surface parallel to the top cover, and a distance from a center of the shaft hole to the bottom surface of the side cover, and a rearward extending amount of the bottom surface from the center of the shaft hole, are both substantially equal to about half a chain pitch.
Preferably, a protrusion is formed on an inner surface of the side cover, and a dimension between protrusions on two side covers is substantially equal to a distance between outer surfaces of pin links of the chain.
The chain cover of this invention has its top cover supported by roller links of the chain to directly bear a load of transported articles on the roller links. Thus, it is unnecessary to increase an amount of insertion of coupling pins of the chain into the shaft holes. An amount of insertion sufficient to obtain an engaging force, required to prevent the chain cover from coming off the chain, is sufficient. The chain cover of this invention can be used, without any problems, with or a general-purpose (standard) roller chain in which a protruding amount of coupling pins is small.
Since an amount of insertion of the coupling pins into the shaft holes can be small, the chain cover can be easily attached and detached to and from the chain.
Further, since a coupling pin is engaged in the shaft holes, only one kind of chain cover is necessary. The chain cover can be attached and detached without severe restriction.
With the chain cover, in which the distance from the center of the shaft holes to the bottom surfaces, and the rearward extending amount of the bottom surfaces from the center of the shaft holes, are about half the chain pitch, bending restriction of the chain by such chain covers is relaxed. Thus, it is possible to bend any portion of the chain at an angle of 90 degrees even after the chain covers have been fit to the chain.
In the an arrangement in which a protrusion of a small area is formed on an inner surface of each side cover, a contact area of the inner surface of each side cover with the chain decreases, so that an increase in bending resistance due to friction with the chain cover can be suppressed.